The present invention relates to an operating circuit for a low-pressure discharge lamp. It specifically concerns the behavior of a low-pressure discharge lamp immediately after ignition of the discharge in a starting phase, and also a starting circuit matched to this behavior.
A particular known feature of low-pressure discharge lamps containing Hg is that the luminous flux produced in the discharge is highly dependent on the temperature of the lamp. For the user, this means that, after it is switched on, the lamp provides a noticeably lower luminous flux for a certain time than when it is being operated continuously. This starting behavior is naturally irritating; however, in the field of lamps containing Hg, it has not been possible to remedy this to date with measures concerning the physics of the lamp itself.
One feasible way is illustrated in German Patent Specification 195 46 588.1 and corresponding U.S. Pat. No. 5,828,187. In this document, the difficulty described with the starting behavior of a low-pressure discharge lamp containing Hg has been tackled by increasing the lamp-current nominal value of a control IC that regulates the lamp current in operation during the starting phase. For further details, you are referred to the document.
In practice, various difficulties have arisen with such operating circuits. In particular, increased numbers of failures have been found.
The invention is thus based on the technical problem of further developing an operating circuit in terms of improved reliability and improved operating characteristics.